In my U.S. Pat. No. 3,982,610, I disclosed a disk brake for wheels of ground or air vehicles and especially of motorcycles, of the type in which at least one brake disk connects the actual hub of the wheel with the spokes carrying flange of the wheel itself, and in which at least one non-rotating plate, provided with friction pads, is slidable along the wheel axis in order to establish or remove the braking engagement between said friction pads and said disk, under the opposing action of fluid pressure control means and of spring return means, said disk brake being characterized in that the braking surface of the disk is a conical surface, with the axis coinciding with the wheel axis, and that the friction pads are carried by the plate, so as to lie on a conical surface mating with the disk braking surface, with which they are designed to be engaged.